initial support for conditional filenames (#1394)

docs/configuration.rst

@@ -97,6 +97,28 @@ Description
     a valid filename extension.
 
 
+extractor.*.filename-conditions
+-------------------------------
+Type
+    ``object``
+Example
+    .. code:: json
+
+        {
+            "extension == 'mp4'"        : "{id}_video.{extension}",
+            "extension in ('zip','rar')": "{id}_archive.{extension}",
+            "'nature' in title"         : "{id}_{title}.{extension}"
+        }
+Description
+    An object containing Python expressions mapping to the
+    filename format strings to use.
+
+    When none of the given conditions match, `extractor.*.filename`_ is used.
+
+    Expressions are evaluated in the order as specified in Python 3.6+
+    and in an undetermined order in Python 3.4 and 3.5.
+
+
 extractor.*.directory
 ---------------------
 Type

gallery_dl/util.py

@@ -756,6 +756,7 @@ class PathFormat():
 
     def __init__(self, extractor):
         filename_fmt = extractor.config("filename")
+        filename_conditions = extractor.config("filename-conditions")
         if filename_fmt is None:
             filename_fmt = extractor.filename_fmt
 
@@ -770,6 +771,14 @@ class PathFormat():
 
         kwdefault = extractor.config("keywords-default")
         try:
+            if filename_conditions:
+                self.build_filename = self.build_filename_conditional
+                self.filename_conditions = [
+                    (compile_expression(expr),
+                     Formatter(fmt, kwdefault).format_map)
+                    for expr, fmt in filename_conditions.items()
+                ]
+
             self.filename_formatter = Formatter(
                 filename_fmt, kwdefault).format_map
         except Exception as exc:
@@ -933,6 +942,19 @@ class PathFormat():
         except Exception as exc:
             raise exception.FilenameFormatError(exc)
 
+    def build_filename_conditional(self):
+        kwdict = self.kwdict
+
+        try:
+            for condition, formatter in self.filename_conditions:
+                if condition(kwdict):
+                    break
+            else:
+                formatter = self.filename_formatter
+            return self.clean_path(self.clean_segment(formatter(kwdict)))
+        except Exception as exc:
+            raise exception.FilenameFormatError(exc)
+
     def build_path(self):
         """Combine directory and filename to full paths"""
         if self._create_directory:

gallery_dl/version.py

@@ -6,4 +6,4 @@
 # it under the terms of the GNU General Public License version 2 as
 # published by the Free Software Foundation.
 
-__version__ = "1.17.6-dev"
+__version__ = "1.18.0-dev"